The man that is thrown off the flamethrower and killed by the infected birds walks past Claire and the others when they discuss journeying to Alaska.
(at around 38 mins) When crow attacks and the bus hits the pole, the pole breaks and falls down. In the next shot the pole is still half-intact, stuck to the bus.
(at around 2 mins) The opening scene in which Alice is naked in the shower shows her with no makeup. Yet, upon wearing the red dress she is wearing red lipstick. Then, in subsequent shots she is wearing no lipstick again.
(at around 1h) While Carlos is crawling under the truck his pistol's slide is forward, however when he tries to fire and we hear clicking, the slide is locked back indicating it is empty.
(at around 18 mins) When Alice shoots "Stevie" through the head with an arrow, there is blood splatter on the truck after he is hit. After checking the pumps, Alice looks at him a second time and the blood splatter has vanished.
(at around 1h 3 mins) When Claire grabs a lever action rifle to shoot the zombie trying to bite Mikey, after firing several shots we see her grabbing more ammo to reload the rifle, however the cartridges (in addition to being obvious stage blanks) she grabs are rimless pistol cartridges, which would not work in a lever action rifle. Come lever action rifles are chambered to fire pistol rounds, but only ones that have rimmed cartridges, the action in a lever action rifle needs a extended rim to grab onto.
Alice uses Sony ICF-SW12 Shortwave World Band Receiver Travel Radio at the beginning of a movie on her bike. This radio lacks scanner function and frequency coverage to receive mobile bands (CB/UHF/VHF).
This means the only way for her to catch KLKB broadcast would be driving with one hand on the radio constantly turning tuning dial.
She wouldn't be unable to hear convoy broadcast call at all.
At about minute 53 when they arrive in Las Vegas, the welcome sign says 'welcome to fantastic Las Vegas' but it should say 'welcome to fabulous Las Vegas'
In the council chambers, Wesker's glasses reflect the room around him. This isn't a mistake - all council chambers are identical, and Wesker's holographic cameras would pick up the reflection of his table - as well as the reflections of the other holograms in the room during a meeting.
(at around 41 mins) After Alice uses her powers to kill the crows, Dr. Isaacs uses 3 satellites to locate her - as evidenced by the display on his computer monitor. Three smaller circles, presumably satellites, centered around a larger circle, presumably the radius of her psionic ability - even though we only see one satellite in orbit. Even if the satellites are not sensitive to psionic bursts (though they should be, since the AI in the Umbrella facility claims to have detected them), Project Alice has several implants which allow Umbrella to track and control her.
(at around 1h 26 mins) At the start of the final scene in Tokyo, there are rats in the street. As the camera descends through the street, one of the rats actually goes in front of the ground revealing that the street is actually a cut-away set.
(at around 18 mins) When Alice comes across the empty gas station she aims her cross bow at the attendant zombie "Stevie" using a basic reflex sight on the bow, yet in the scene it shows that she has managed to magnify all the way up to his chest revealing his name. The sight used on the crossbow does not have anywhere near that amount of magnification.
(at around 1h 26 mins) During the scene in which Tokyo appears, there are several Japanese signs that just have random Japanese ideograms completely irrelevant to what should be there.
(at around 59 mins) When the zombies are coming out of the large container, there are tons of them coming out of it but there's no way they could have all fit into the container in the first place.
(at around 1h 27 mins) In the last moments of the film when the camera pans out showing the many clones of Alice. The footage of the awoken clone in the bottom left can be seen reaching the end of the recording and then played in reverse to fill a few extra seconds.
(at around 6 mins) After the Alice clone is killed at the beginning, her body is shown being dumped into a pit with the other dead clones. Even though Dr. Isaacs has been killing the clones for weeks, none of the dead bodies show any decomposition, nor have any of them desiccated (dried out) in the desert heat.
While all of the men look understandably worse for wear in this post-apocalyptic world, all of the women are sporting full faces of perfect makeup, clean untangled hair, and shaved underarms. There is no plausible way these women could look so good and clean given the state of the world.
L.J references the film Brokeback Mountain to Chase in a conversation, a film released in 2005. The apocalypse started around 2002 shortly after the outbreak at Raccoon City. This film takes place 5 years later in present day 2007, which means that the film couldn't have existed in the current timeline.
(at around 34 mins) When Alice walks through the dunes, just before the crow's attack, the cameraman filming her is visible in her glasses.
(at around 56 mins) After the characters arrive in Las Vegas, they park right next to the Paris Casino's Eiffel Tower and the Venetian Casino. In reality, The Venetian is one mile up Las Vegas Blvd (The Strip).
In the beginning the crew including Alice head through Salt Lake City. The only way to get to Nevada through Salt Lake it to drive mostly north and head in through Wendover. Later on in the movie they talk about gas and how they need to go to Vegas to get gas. The driver said he had about 100 miles left on his truck. It would have taken over 100 miles to get to Vegas from where they were. It takes six hours to get to Vegas from Salt Lake City.
At approximately 46 minutes when Carlos and Alice reunite, Carlos mentions Detroit as the city in which they last saw each other. That location, Resident Evil: Apocalypse (the previous film) takes place in the fictional Raccoon City. However, Detroit is used for the exterior, establishing shots for Raccon City in the Resident Evil films.
At the end of the movie, all survivors go to Umbrella HQ to get the helicopter. In fact it's very risky to bring everyone. Bringing noncombat personnel to that region risks the operation since they could have been killed or their presence decreases effectiveness of the heroes since they also should over watch the civilians. Since helicopter is a highly maneuverable vehicle it would be wiser to leave those civilians at a safe distance, go and get the helicopter and come and pick them up.